The back of the house is not constructed with pressure treated wood and directly on the ground. So options are to start digging myself or pay someone to lift the house and put a proper basement under it. The 50,000 is for a house lifting, new basement etc. [\quote]
Hi frugal,
If your house was built on timbers on the ground, then I understand the $50,000 now. It is a big job to lift an existing damaged structure, and do all the work required. Houses are built from the bottom-up. But this type of work is done the other-way 'round. I have done jacking and major sill and joist work on a house that was initially built on timbers. It had been raised and settled down on knee walls years before I worked on it. But a lot of the damage from soil contact had not been repaired - sills collapsing, joists compressing on the outer ends. So I jacked, replaced, or sistered everything affected. Long term, keeping wood dry and away from the soil is the only solution.
A full basement doesn't have to be the solution, unless you want the space. A crawlspace can solve problems. Short concrete sidewalls, sitting on footings below the frost line, concrete piers for girder support, and a concrete floor for the crawlspace. The concrete floor can be thinner than a basement floor, but should have reinforcing mesh, and be poured over a continuous 6 mil thick plastic vapor barrier. Crawl spaces can get into trouble with venting, depending on where in the country you are. As they are not living space, their needs are easily forgotten about. In northern climates, there should be airflow from outside in the warmer months. In colder months, they can be closed up, if the moisture barrier is pretty good.
I also noticed the build costs per square foot you mentioned! An expensive area... and an expensive area almost always means expensive labor costs too. In a major job like that, SOMEONE needs to be responsible for the finished job, and its trouble-free survival. Which means someone who has done it in your area before, who has a good track record over the years. Who can handle the unexpected, as with existing construction unexpected is always discovered during the job. And those people are not bargain basement (no pun intended!). And they use subcontractors that they trust and have built a relationship with over the years. Avoid lowballers!
Good luck with your project